1. Field of the invention
The present invention relates to a choke valve provided with a carburetor, and particularly to a choke valve provided with a relief valve in the choke valve body of the carburetor.
2. Description of Related Art
A conventional example of such a choke valve provided with a relief valve is disclosed in Japanese Patent Laid-open No. Sho. 58-165555, and is shown in FIG. 14 of the present invention.
A throttle valve 04 is arranged at a downstream side of a venturi section 03 in an intake passageway 02 of the carburetor body 01. A choke valve 05 is arranged at the upstream side of the venturi section 03.
The choke valve 05 is attached with screws to a choke shaft 06 that is rotatably constructed in the intake passageway 02.
A relief window 05a is formed through the choke valve 05. This relief window 05a opens and closes the relief valve 08.
The relief valve 08 is formed as an elastic plate, and a base end part is attached to the choke valve 05 using screws 09 etc. The relief window 05a is closed when the relief valve is not subject to any external force.
In the relief valve 08 provided in the above described choke valve 05, a base end part is attached to the choke valve 05 using screws 09 etc. which avoid the choke shaft 06. Therefore, the screws 07 for attaching the choke valve 05 to the choke shaft 06 are necessary, as well as a separate attachment member such as screws 09 for attaching the relief valve 08 to the choke valve 05. Therefore, there are a large number of manufacturing steps and the number of components is increased. Accordingly, the manufacturing cost is increased.
In addition, because of the large number of components, the overall weight of the choke valve 04 having a relief valve attached thereto is heavy.
If the choke valve 04 is heavy, it can not operate smoothly. As a result, the choke valve 04 crashes into a seat surface when it is completely closed, leading to abrasion of the seat surface.
Furthermore, because the base end side of the relief valve 08 is attached to the choke valve 05 using screws 09 etc. such that the choke shaft 06 is avoided, the relief window 05a can not be located close to the choke shaft 06 which is the rotational axis of the choke valve 05. Therefore, the relief passageway can not be kept wide.